WO2006/043069 Al discloses continuous extrusion apparatus having a rotatable wheel formed with two identical circumferential grooves outwardly bounded by arcuate tooling discharging through radial exit apertures to an extrusion chamber positioned around a portal mandrel and means arranged continuously to supply a core through the mandrel whilst aluminium based sheathing is extruded from the extrusion chamber around the core to form a cable being discharged to a roller corrugator arranged to form a helical corrugation on the sheath.